When a power supply system is constructed, important challenges are not only to safely expand a power transmission network but also to construct the system so that a large quantity of natural energy can be introduced into the system in the future. Therefore, as a new power network, a power network system called “digital grid” (registered trademark) has been proposed (Patent Literatures 1 and 2).
The digital grid (registered trademark) is a power network system in which a power network is sub-divided into small cells and these cells are connected with each other in an asynchronous manner. The size of each power cell ranges from a smaller one such as a cell corresponding to one house, one building, or one commercial facility to a larger one such as a cell corresponding to one prefecture or one municipality. Each power cell includes loads and, in some cases, a generator facility and/or a power storage facility. Examples of the generator facility include generator facilities using natural energy such as a solar generator, an aerogenerator, and a geothermal power plant.
Power cells are asynchronously connected to freely generate power inside each power cell or smoothly interchange power between power cells. That is, even when a plurality of power cells are connected with other, a voltage, a phase and a frequency of power used in each power cell are out of synchronization with other power cells. FIG. 23 is a view illustrating an example of a power network system 810. In FIG. 23, a core system 811 feeds core power from a large-scale power plant 812. Further, a plurality of power cells 821 to 841 are installed. Each of the power cells 821 to 824 includes loads such as a house 831 and a building 832, power generation facilities (e.g. a solar panel 833 and a wind power generator 834) and a power storage facility (e.g. a storage battery 835).
In addition, in this description, power generation facilities and power storage facilities will be collectively referred to as distributed power supplies.
Further, the power cells 821 to 824 include power routers 841 to 844 which are connections (connection ports) for connecting with other power cells and the core system 811, respectively. The power routers 841 to 844 include a plurality of legs. (For convenience of the drawings, reference numerals of the legs will not be indicated in FIG. 23, and white circles attached to the power routers 841 to 844 are connection terminals of the respective legs.) In this regard, a leg includes a connection terminal and a power converting unit, and each leg is allocated an address.
In addition, power conversion in a leg refers to converting an alternating current into a direct current or a direct current into an alternating current, or changing the voltage, the frequency or the phase of power.
All power routers 841 to 844 are connected to a management server 850 through a communication network 860, and the management server 850 integrally controls operations of all power routers 841 to 844. For example, the management server 850 instructs each of the power routers 841 to 844 to feed power or receive power per leg. Thus, power is interchanged between power cells through the power routers 841 to 844.
By interchanging power between power cells, for example, one power generation facility (e.g. the solar panel 833 or the wind power generator 834) or one power storage facility (e.g. the storage battery 835) can be shared between a plurality of power cells. When power cells mutually interchange extra power, a power demand and supply balance can be stably kept while substantially reducing facility cost.